The present application relates to a light oscillation device emitting laser light and a recording device using the light oscillation device.
In recent years, with the advance of IT in society, there is a further demand for high capacity and high speed. For this reason, as media for delivery of information, like wireless communication, optical communication using not only electromagnetic waves in, for example, a 2.4 GHz band or a 5 GHz band but also light in, for example, a 1.5 μm band (to several hundreds of THz range) has been rapidly disseminated.
In addition, since the delivery of information using light is applied to optical communication using, for example, optical fiber and further to recording and reproducing information to and from a recording medium, the optical information technique is an important base for supporting the progress of the information society in the future.
A light source which oscillates specific pulses is used to deliver and record information using light. Particularly, for the high capacity and high speed of the communication, the recording, and the reproduction, light sources with high output and short pulses are necessary, and, as light sources which satisfy them, various kinds of semiconductor lasers have been studied and developed.
For example, when a recording device of an optical disc performs reproduction during use of a single mode laser, noises occur due to interference of an optical system, and an oscillation wavelength and an output vary or noises occur due to variation in temperature.
For this reason, a method has been performed in which a laser has multiple modes through modulation using an external high frequency module, and the output variation due to the variation in temperature or light returning to the optical disc is suppressed. However, in this method, a device becomes large and costs increase with the addition of the high frequency module.
In contrast, a self oscillation semiconductor laser flashes at high frequency and directly oscillates in the multimode, it is possible to suppress the output variation without the high frequency module.
For example, the present inventors implement a light source capable of realizing the pulse width of 30 ps and the oscillation output of 2.4 W at the frequency of 0.9 GHz using a self oscillating GaN blue-violet semiconductor laser (refer to Takao Miyajima, Hideki Watanabe, Masao Ikeda and Hiroyuki Yokoyama, Applied Physics Letters 94, 161103 (2009)).
This semiconductor laser is a BS (bisectional) type self oscillation semiconductor laser which includes a gain section and a saturable absorber section.
In the semiconductor laser, a reverse bias voltage is applied to the saturable absorber section. At this time, a current is injected into the gain section, and thereby laser light having, for example, the wavelength of 407 nm is emitted.